HIV-associated nephropathy (HIVAN) is now the third leading cause of renal failure in African Americans, the most common cause of chronic renal failure in HIV-1 infected individuals and renal disease is now the fourth leading cause of death in these patients. Accumulating evidence supports a direct role of HIV-1 infection of renal glomerular and tubule epithelial cells in HIVAN pathogenesis. Furthermore, quasispecies analysis of HIV-1 envelope sequences simultaneously derived from renal epithelial cells and peripheral blood mononuclear cells show renal-specific subclusters consistent with active replication of HIV-1 in the renal compartment. In vitro and transgenic mouse model data suggest that direct expression of HIV-1 genes, particularly nef, in renal epithelium can produce phenotypic changes and alterations in expression of cell genes involved in proliferation and differentiation that are consistent with changes associated with HIVAN. Project 2 will further define the direct role of infection of renal epithelial cells in HIVAN pathogenesis. To determine if renal epithelial infection alone can account for the disease, renal tissue will be examined from HIV-infected patients who have an alternative etiology of renal disease. This will include those of African descent as well as Caucasians. Examination of tissue will include in situ DNA PCR and confirmatory laser dissection of epithelial cells with PCR amplification of HIV sequences. To further our understanding of viral lentry into this unique compartment, we will phenotypically characterize the HIV-1 envelopes directly obtained from renal epithelium by laser capture dissection. In light of our previous published work and preliminary data demonstrating the effects of Nef and, to a lesser degree, Vpr on podocytes, we will use transgeneic mouse modeling to study the contribution of individual gene products expressed in specific cell types to pathogenesis. Targeted expression will be achieved either through direct expression of the transgene from site-specific promoters or the use of conditional transgenic constructs. Furthermore, nef sequences derived directly from renal epithelium will be genotypically and phenotypically characterized to determine if unique polymorphisms are associated with the development of HIVAN. The proposed studies should provide critical information regarding the role of epithelial infection in HIVAN pathogenesis and the interaction of HIV-1 with this unique reservoir and will impact on therapeutic interventions to prevent this devastating complication.